1. Field of the Invention
The present invention relates to a surgical stapler for suturing tissue, and more particularly, to a surgical stapler that enables the user to sense clearly the suturing operation, that is, the completion of the bending of the staple.
2. Background of the Invention
In surgical operations, metal staples are bent to suture shut an incision. As that which is used for this purpose, the surgical staplers described in Japanese Laid-Open Patent Application Publication No. Heisei 05-3879 and Japanese Laid-Open Patent Application Publication No. 2000-217829 are conventionally known.
FIG. 3 shows the process of bending a staple using these conventionally known surgical staplers.
A staple 1 penetrates the tissue and remains imbedded in the tissue until the incision heals. Accordingly, it is important that the staples be both sufficiently strong and do not adversely affect the tissue, and for these reasons austenitic stainless steel, which does not rust, is used for the staple 1. The staple 1 consists of rounded wire with a diameter of approximately 0.5 mm that is cut and then bent in the shape of a “C”. The straight portion of the staple 1 is called the crown 1a and the portions bent from both ends of the crown 1a are called the legs 1b. In order to pierce tissue easily the tips of the legs 1b are pointed.
FIG. 3A shows an initial state, with a ram 3 moving toward an anvil 4 and the staple 1 held between the anvil 4 and the tips of pressure armatures 3a formed on both sides of a concave part 3b of the ram 3.
FIG. 3B shows an intermediate state, in which the ram 3 further descends, the anvil 4 reaches the entrance to the concave part 3b, and the staple 1 is partially bent by the armatures 3a. 
FIG. 3C shows a final state, in which the ram 3 continues to descend, the anvil 4 enters the concave part 3b and presses against the crown 1a of the staple 1 at the concave part bottom surface 3b′, and the staple 1 is bent at right angles at both ends of the anvil 4 in the direction of the breadth of the anvil 4, closing the staple 1. This state is the state in which the bending of the staple 1 is completed. In this state, the crown 1a indicates the top part of the staple, which is now a rectangular shape.
In the process of moving from the state shown in FIG. 3B to the one shown in FIG. 3C, the tips of the staple 1 enters the tissue, completing one suture. If the incision is a large one, suturing is repeated as many times as needed. It should be noted that, in this specification, the staple in its closed state indicates a state in which, when the staple is bent between the ram and the anvil, the most fully bent portion is completely bent, and includes not only a state in which the tips of the legs 1b of the staple 1 are completely in contact but also are just slightly separated from each other.
The surgical stapler described in Japanese Laid-Open Patent Application Publication No. Heisei 05-3879 arranges a plurality of C-shaped staples in an aligned state astride the top of the anvil plate inside the body of the stapler and pushes the staples forward with a torsion spring. The forward edge of the anvil plate is the anvil, with the ram disposed substantially perpendicular to the anvil. The anvil is fixed, and the ram is advanced toward and withdrawn from the anvil by a rotary trigger, bending the staple fed to the front of the anvil into its final rectangular shape.
The surgical stapler described in Japanese Laid-Open Patent Application Publication No. 2000-217829 has a magazine containing a plurality of staples in a state of alignment, and a ram and an anvil that are moved in tandem by a trigger. Operating the trigger causes the ram and the anvil to pick out a single staple, hold it, and move together to bend the staple into its final form.
FIG. 4 is a diagram showing an external view of a surgical stapler 10 described in Japanese Laid-Open Patent Application Publication No. Heisei 05-3879. The same ram and anvil as shown in FIGS. 3A, 3B and 3C are contained in the stapler body 11, together with a plurality of staples 1. As the trigger 12 approaches the body 11, the forward edges of the ram and the anvil approach each other within the body 11, bending the staple held at the front of the anvil into its final form.
FIG. 5 is a diagram showing the structure of a surgical stapler 20 described in Japanese Laid-Open Patent Application Publication No. 2000-217829. The surgical stapler 20 comprises a magazine 22 containing a plurality of staples 1 in a state of alignment, a ram 23, an anvil 24 and a trigger 25 inside the staple body 26.
The trigger 25 revolves around a revolving shaft 27 provided on the body 26. A hole that engages the revolving shaft 27 is a slot 28. A pin 29 and a V-shaped groove 30 guide the trigger 25 as it revolves. Such a structure enables the trigger 25 to move and revolve with respect to the body 26 of the stapler, such that when force is applied to the trigger 25, the trigger can rotate as its axis of rotation moves toward the ram 23. As a result, the distance from the axis of rotation of the trigger 25 to the grip widens, enabling a large torque to be generated with a relatively small force.
However, the surgical staplers described in Japanese Laid-Open Patent Application Publication Nos. 5-3879 and 2000-217829 suffer from the drawback that the user gets no particular sensation indicating that the staple has been bent into its final form when that action is completed as shown in FIG. 3C. At most, just prior to completion of the bending of the staple into its final form, the movement of the trigger 25 becomes easier than it has been up to that point, and then becomes harder, which is the only indication that the suture is completed. However, after the movement of the trigger 25 gets easier it is not easy to tell how hard the movement will become, and it is easy to think that the suture is completed when in fact it is not.